Trabectedin Enhances Oncolytic Virotherapy by Reducing Barriers to Virus Spread and Cytotoxic Immunity in Preclinical Pediatric Bone Sarcoma.

We previously reported that the DNA alkylator and transcriptional-blocking chemotherapeutic agent trabectedin enhances oncolytic herpes simplex viroimmunotherapy in human sarcoma xenograft models, though the mechanism remained to be elucidated. Here we report trabectedin disrupts the intrinsic cellular anti-viral response which increases viral transcript spread throughout the human tumor cells. We also extended our synergy findings to syngeneic murine sarcoma models, which are poorly susceptible to virus infection. In the absence of robust virus replication, we found trabectedin enhanced viroimmunotherapy efficacy by reducing immunosuppressive macrophages and stimulating granzyme expression in infiltrating T and NK cells to cause immune-mediated tumor regressions. Thus, trabectedin enhances both the direct virus-mediated killing of tumor cells and the viral-induced activation of cytotoxic effector lymphocytes to cause tumor regressions across models. Our data provide a strong rationale for clinical translation as both mechanisms should be simultaneously active in human patients.

The quest for effective immunotherapies against malignant peripheral nerve sheath tumors: Is there hope?

Immune-based therapies represent a new paradigm in the treatment of multiple cancers, where they have helped achieve durable and safe clinical responses in a growing subset of patients. While a wealth of information is available concerning the use of these agents in treating the more common malignancies, little has been reported about the use of immunotherapies against malignant peripheral nerve sheath tumors (MPNSTs), a rare form of soft tissue sarcoma that arises from the myelin sheaths that protect peripheral nerves. Surgical resection has been the mainstay of therapy in MPNSTs, but the recurrence rate is as high as 65%, and chemotherapy is generally ineffective. The immune contexture of MPNSTs, replete with macrophages and a varying degree of T cell infiltration, presents multiple opportunities to design meaningful therapeutic interventions. While preliminary results with macrophage-targeting strategies and oncolytic viruses are promising, identifying the subset of patients that respond to immune-based strategies will be a milestone. As part of our effort to help advance the use of immunotherapy for MPNSTs, here we describe recent insights regarding the immune contexture of MPNSTs, discuss emerging immune-based strategies, and provide a brief overview of potential biomarkers of response.

Oncolytic virus-driven immune remodeling revealed in mouse medulloblastomas at single cell resolution.

Oncolytic viruses, modified for tumor-restricted infection, are a promising cancer immunotherapeutic, yet much remains to be understood about factors driving their activity and outcome in the tumor microenvironment. Here, we report that oncolytic herpes simplex virus C134, previously found to exert T cell-dependent efficacy in mouse models of glioblastoma, exerts T cell-independent efficacy in mouse models of medulloblastoma, indicating this oncolytic virus uses different mechanisms in different tumors. We investigated C134's behavior in mouse medulloblastomas, using single cell RNA sequencing to map C134-induced gene expression changes across cell types, timepoints, and medulloblastoma subgroup models at whole-transcriptome resolution. Our work details substantial oncolytic virus-induced transcriptional remodeling of medulloblastoma-infiltrating immune cells, 10 subpopulations of monocytes and macrophages collectively demonstrating M1-like responses to C134, and suggests C134 be investigated as a potential new therapy for medulloblastoma.

Genetically modified IL2 bone-marrow-derived myeloid cells reprogram the glioma immunosuppressive tumor microenvironment.

Gliomas are one of the leading causes of cancer-related death in the adolescent and young adult (AYA) population. Two-thirds of AYA glioma patients are affected by low-grade gliomas (LGGs), but there are no specific treatments. Malignant progression is supported by the immunosuppressive stromal component of the tumor microenvironment (TME) exacerbated by M2 macrophages and a paucity of cytotoxic T cells. A single intravenous dose of engineered bone-marrow-derived myeloid cells that release interleukin-2 (GEMys-IL2) was used to treat mice with LGGs. Our results demonstrate that GEMys-IL2 crossed the blood-brain barrier, infiltrated the TME, and reprogrammed the immune cell composition and transcriptome. Moreover, GEMys-IL2 extended survival in an LGG immunocompetent mouse model. Here, we report the efficacy of an in vivo approach that demonstrates the potential for a cell-mediated innate immunotherapy designed to enhance the recruitment of activated effector T and natural killer cells within the glioma TME.

Opportunities and challenges of combining adoptive cellular therapy with oncolytic virotherapy.

The use of oncolytic viruses (OVs) and adoptive cell therapies (ACT) have independently emerged as promising approaches for cancer immunotherapy. More recently, the combination of such agents to obtain a synergistic anticancer effect has gained attention, particularly in solid tumors, where immune-suppressive barriers of the microenvironment remain a challenge for desirable therapeutic efficacy. While adoptive cell monotherapies may be restricted by an immunologically cold or suppressive tumor microenvironment (TME), OVs can serve to prime the TME by eliciting a wave of cancer-specific immunogenic cell death and inducing enhanced antitumor immunity. While OV/ACT synergy is an attractive approach, immune-suppressive barriers remain, and methods should be considered to optimize approaches for such combination therapy. In this review, we summarize current approaches that aim to overcome these barriers to enable optimal synergistic antitumor effects.

Myeloid cell heterogeneity in the tumor microenvironment and therapeutic implications for childhood central nervous system (CNS) tumors.

Central nervous system (CNS) tumors are the most common type of solid tumors in children and the leading cause of cancer deaths in ages 0-14. Recent advances in the field of tumor biology and immunology have underscored the disparate nature of these distinct CNS tumor types. In this review, we briefly introduce pediatric CNS tumors and discuss various components of the TME, with a particular focus on myeloid cells. Although most studies regarding myeloid cells have been done on adult CNS tumors and animal models, we discuss the role of myeloid cell heterogeneity in pediatric CNS tumors and describe how these cells may contribute to tumorigenesis and treatment response. In addition, we present studies within the last 5 years that highlight human CNS tumors, the utility of various murine CNS tumor models, and the latest multi-dimensional tools that can be leveraged to investigate myeloid cell infiltration in young adults and children diagnosed with select CNS tumors.

Pediatric versus adult high grade glioma: Immunotherapeutic and genomic considerations.

High grade gliomas are identified as malignant central nervous tumors that spread rapidly and have a universally poor prognosis. Historically high grade gliomas in the pediatric population have been treated similarly to adult high grade gliomas. For the first time, the most recent classification of central nervous system tumors by World Health Organization has divided adult from pediatric type diffuse high grade gliomas, underscoring the biologic differences between these tumors in different age groups. The objective of our review is to compare high grade gliomas in the adult versus pediatric patient populations, highlighting similarities and differences in epidemiology, etiology, pathogenesis and therapeutic approaches. High grade gliomas in adults versus children have varying clinical presentations, molecular biology background, and response to chemotherapy, as well as unique molecular targets. However, increasing evidence show that they both respond to recently developed immunotherapies. This review summarizes the distinctions and commonalities between the two in disease pathogenesis and response to therapeutic interventions with a focus on immunotherapy.

Leveraging gene therapy to achieve long-term continuous or controllable expression of biotherapeutics.

T cells redirected to cancer cells either via a chimeric antigen receptor (CAR-T) or a bispecific molecule have been breakthrough technologies; however, CAR-T cells require individualized manufacturing and bispecifics generally require continuous infusions. We created an off-the-shelf, single-dose solution for achieving prolonged systemic serum levels of protein immunotherapeutics via adeno-associated virus (AAV) gene transfer. We demonstrate proof of principle in a CD19+ lymphoma xenograft model using a single intravenous dose of AAV expressing a secreted version of blinatumomab, which could serve as a universal alternative for CD19 CAR-T cell therapy. In addition, we created an inducible version using an exon skipping strategy and achieved repeated, on-demand expression up to at least 36 weeks after AAV injection. Our system could be considered for short-term and/or repeated expression of other transgenes of interest for noncancer applications.

Cardiorespiratory management of Duchenne muscular dystrophy: emerging therapies, neuromuscular genetics, and new clinical challenges.

The life-limiting complications of Duchenne muscular dystrophy (DMD) include loss of lung function and progressive cardiomyopathy; when patients are treated with assisted ventilation, cardiac function becomes the main determinant of survival. Therapy for DMD is changing rapidly, with the emergence of new genetic and molecular therapeutic options, the proliferation of which has fostered the perception that DMD is a potentially curable disease. However, data for respiratory and cardiac outcomes are scarce and available evidence is not uniformly positive. Patients who share a dystrophin (DMD) genotype can have highly divergent cardiorespiratory phenotypes; genetic modifiers of DMD gene expression are a probable cause of respiratory and cardiac phenotypic variability and discordance. In this Personal View, we provide an overview of new and emerging DMD therapies, highlighting the limitations of current research and considering strategies to incorporate cardiorespiratory assessments into clinical trials. We explore how genetic modifiers could be used to predict cardiorespiratory natural history and how manipulation of such modifiers might represent a promising therapeutic strategy. Finally, we examine the changing role of respiratory physicians, cardiologists, and intensive care clinicians on the frontline of a challenging new clinical landscape.

Clinical outcomes and efficacy of stereotactic body radiation therapy in children, adolescents, and young adults with metastatic solid tumors.

OBJECTIVE: The objective of this study is to report disease outcomes and toxicity with the use of stereotactic body radiation therapy (SBRT) in the treatment of pediatric metastatic disease. METHODS: All pediatric and adolescent young adult (AYA) patients' who received SBRT were included between the years 2000 and 2020. Study endpoints included local control (LC), progression-free survival (PFS), overall survival (OS), cumulative incidence (CI) of death or local failure and toxicity. The end points with respect to survival and LC were calculated using the Kaplan-Meier estimate. The cumulative incidence of local failure was calculated using death as a competing risk. RESULTS: 16 patients with 36 lesions irradiated met inclusion criteria and formed the study cohort. The median OS and PFS for the entire cohort were 17 months and 15.7 months, respectively. The 1 year OS for the entire cohort was 75%. The 6- and 12 month local control was 85 and 78%, respectively. There were no local failures in irradiated lesions for patients who received a BED10≥100 Gy. Patients who were treated with SBRT who had ≤5 metastatic lesions at first recurrence had a superior 1 year OS of 100 vs 50% for those with >5 lesions. One patient (6.3%) experienced a Grade 3 central nervous system toxicity. CONCLUSION: LC was excellent with SBRT delivered to metastatic disease, particularly for lesions receiving a BED10≥100 Gy. High-grade toxicity was rare in our patient population. Patients with five or fewer metastatic sites have a significantly better OS compared to >5 sites. ADVANCES IN KNOWLEDGE: This study demonstrates that SBRT is safe and efficacious in the treatment of pediatric oligometastatic disease.

Immunotherapies for Pediatric Solid Tumors: A Targeted Update.

There are encouraging signs in our collective progress to leverage the immune system to treat pediatric cancers. Here, we summarize interim successes in cancer immunotherapy and opportunities to translate from the adult world to pediatrics, and highlight challenges that could benefit from additional development, focusing on solid tumors. Just a decade ago, other than antibodies targeting disialoganglioside (GD2) in neuroblastoma, pediatric cancer immunotherapy was mostly relegated to obscure preclinical studies in a few academic labs. Today there are numerous clinical trials of a variety of antibody, cellular, gene, and viral therapies and vaccines designed to either promote antitumor immunity or specifically attack validated immunotherapy targets. Understanding those targets and their pediatric relevance is paramount. While much work is underway to evaluate the utility of numerous immunologic targets, the lack of regulatory approvals is emblematic of the challenges that remain. Herein we focus our review on the most promising targeted immunotherapies in clinical trials for children.

An open-label multi-center phase 1 safety study of BXQ-350 in children and young adults with relapsed solid tumors, including recurrent malignant brain tumors.

Background: BXQ-350 is a novel anti-neoplastic agent composed of saposin C (SapC) and phospholipid dioleoylphosphatidyl-serine sodium (DOPS) that selectively binds tumor cell phosphatidylserine (PS), inducing apoptosis. BXQ-350 has demonstrated preclinical antitumor effects in high-grade gliomas (HGG) and clinical activity in adult patients with recurrent HGG. Methods: A phase 1 study was conducted in pediatric patients with relapsed/refractory solid tumors, including recurrent brain tumors. Primary objectives were to characterize safety and determine maximum tolerated dose (MTD) and preliminary antitumor activity. Sequential dose cohorts were assessed up to 3.2 mg/kg using an accelerated titration design. Each cycle was 28 days; dosing occurred on days 1-5, 8, 10, 12, 15, and 22 of cycle 1, and day 1 of subsequent cycles, until disease progression or toxicity. Results: Nine patients, median age 10 years (range: 4-23), were enrolled. Seven patients (78%) had central nervous system (CNS) and two (22%) had non-CNS tumors. Eight patients completed cycle 1. No dose limiting toxicity (DLT) or BXQ-350-related serious adverse events (SAEs) were observed. Six patients experienced at least one adverse event (AE) considered possibly BXQ-350-related, most were grade ≤2. One patient with diffuse intrinsic pontine glioma experienced stable disease for 5 cycles. The study was terminated after part 1 to focus development on the frontline setting. Conclusion: No DLTs or BXQ-350-related SAEs were reported, and the maximal planned dose of 3.2 mg/kg IV was tolerable. Limited safety and efficacy data support continued BXQ-350 development in pediatric HGG; however, early discontinuations for progression suggest novel therapies be assessed at earlier disease stages.

Endogenous retrovirus envelope as a tumor-associated immunotherapeutic target in murine osteosarcoma.

Osteosarcoma remains one of the deadliest cancers in pediatrics and young adults. We administered two types of immunotherapies, oncolytic virotherapy and immune checkpoint inhibition, to two murine osteosarcoma models and observed divergent results. Mice bearing F420 showed no response, whereas those with K7M2 showed prolonged survival in response to combination therapy. K7M2 had higher expression of immune-related genes and higher baseline immune cell infiltrates, but there were no significant differences in tumor mutational burden or predicted MHC class I binding of nonsynonymous mutations. Instead, we found several mouse endogenous retrovirus sequences highly expressed in K7M2 compared with F420. T cell tetramer staining for one of them, gp70, was detected in mice with K7M2 but not F420, suggesting that endogenous retrovirus proteins are targets for the anti-tumor immune reaction. Given prior observations of endogenous retrovirus expression in human osteosarcomas, our findings may be translatable to human disease.

The effect of emerging molecular and genetic therapies on cardiopulmonary disease in Duchenne muscular dystrophy.

Gene therapy is an attractive approach being intensively studied to prevent muscle deterioration in patients with Duchenne muscular dystrophy. While clinical trials are only in early stages, initial reports are promising for its effects on ambulation. Cardiopulmonary failure, however, is the most common cause of mortality in Duchenne muscular dystrophy (DMD) patients, and little is known regarding the prospects for gene therapy on alleviating DMD-associated cardiomyopathy and respiratory failure. Here we review current knowledge regarding effects of gene therapy on DMD cardiomyopathy and discuss respiratory endpoints that should be considered as outcome measures in future clinical trials.

Oncolytic Viruses and Their Potential as a Therapeutic Opportunity in Osteosarcoma.

Osteosarcoma remains an unmet medical need. Oncolytic viruses are gaining traction as novel cancer therapeutics. These viruses are either naturally nonpathogenic or engineered to be safe by specific genetic deletions yet retain the ability to infect and kill human cancer cells and elicit anticancer immunity. Some versions are being specifically designed and tested in patients with osteosarcoma, though due to their generalized mechanism of action most are being tested in patients across a broad range of cancer types. The activity of these viruses is impacted not only by the susceptibility of tumor cells to infection but also by the tumor microenvironment (TME) and by tumor immunogenicity. Here we review the field of oncolytic viruses with a particular emphasis on highlighting any available data in preclinical osteosarcoma models or in patients with osteosarcoma. While in general the viruses have been shown safe to administer to patients by a variety of routes, their therapeutic efficacy to date has been limited. Given the low rate of adverse events and the likely absence of long-term side effects, the utility of oncolytic viruses will most likely be realized when used in combination with other agents.